A risk factor is something that increases your likelihood of getting a disease or condition.

Autism can develop
with or without the risk factors listed below. However, the more risk factors that are present, the higher the chances that autism can develop. There is no known way to change your child's risk for autism.

Genetic Factors

Genetics is believed to play a role in the risk of autism. This is because the condition is more common in:

Families

Identical twins

Recent studies have linked deletions in a section of chromosome 16. This chromosome abnormality may account for a small percentage of autism cases.

Sex

Caucasian males are more likely to be affected by autism than females. When girls are affected, they may have more profound symptoms.

Age of Parents

Older parents, such as a woman over age 35, may have a higher risk of having a child with autism.

Medical Conditions

Autism occurs more frequently in children with rare genetic disorders or other medical conditions, including:

Tuberous sclerosis—A rare, multi-system genetic disease. It causes benign tumors to grow in the brain and on other vital organs. The organs include the kidneys, heart, eyes, and skin. It commonly affects the central nervous system. This results in a combination of symptoms. These include
seizures, developmental delay, behavioral problems, skin abnormalities, and
kidney disease
.

Fragile X syndrome
—A hereditary disorder of the X chromosome. It is the most common cause of inherited intellectual disability.

Neurofibromatosis
—A genetic disorder of the nervous system. It causes tumors to grow on the nerves in any part of the body. Neurofibromatosis can also produce other abnormalities. These include changes in the skin and deformed bones.

Phenylketonuria
(PKU)—A genetic disorder of the enzyme that breaks down phenylalanine. Phenylalanine is an amino acid found in certain foods. Without a proper diet, PKU can lead to
intellectual disability
.

Problems during pregnancy or delivery, including
rubella
—Rubella is a mild, highly contagious illness that is caused by a virus. The symptoms are a rash, swollen glands, and joint pain. If a pregnant woman has rubella, it can cause birth defects in her baby.
Other possible risk factors include breech delivery and birth at less than 35 weeks gestation.

Epilepsy
—This term refers to any disorder characterized by recurrent seizures. A seizure can have many symptoms. There may loss of consciousness, staring into space, abnormal jerking of the muscles, or abnormal sensations or emotions.

Rett syndrome—A problem with the development of the nervous syndrome. It is most common in girls.

Smith-Lemli-Opitz—A metabolic disorder caused by a gene mutation. People with the disorder cannot make enough cholesterol.

West syndrome—Causes a specific type of seizure seen in an epilepsy syndrome of infancy
and childhood.

There has been much attention around a link between vaccines and autism. This is partly because of a vaccine preservative called thimerosol. Studies have not found an association between vaccines and the development of autism.

Revision Information

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.